This invention relates to a synthetic resin container having the rim or legs which project downwardly from the undersurface of the bottom thereof substantially at right angles to the bottom and have thickness and density greater than the other parts of the container and a method and a device for moulding such a container.
Conventional food containers formed of synthetic resin and particularly, of foam synthetic resin such as foam polystyrene have the rim or legs which bulge downwardly from the bottom. However, the bottom rim or legs have the same thickness and density as the other parts of the container such as the side and bottom walls, for example (refer to Laid-Open Japanese Utility Model Application Publication No. 51571/1974, for example). The conventional moulding devices and methods for moulding containers by thermal moulding synthetic resin sheet into a container have been impossible to mould the bottom rim or legs having thickness and density greater than those of the other parts of the container.
The disadvantages of the conventional synthetic resin containers for foods are that since the bottom rim or legs of the container have the same thickness and density as those of the other parts of the container, the container is unstable and tends to fall down easily and that since the bottom rim or legs merely bulge from the container bottom, when boiling water or the like is poured into the container all the parts of the container including the bottom rim or legs are soon heated to a substantially elevated temperature and the high temperature of the boiling water or the like is directly transferred to the user's fingers which contact the bottom rim or legs of the container and thus, the user can not grip the container rim or legs easily.